Physical Properties and Microscopic Observation of Cold-gel Prepared from Soy Protein Isolate

Studies on the Gelation of Soy Protein during Cold Storage Part III

Abstract

Physical properties of cold-gel prepared from heated soy protein isolate were investigated compared with heat-gel and freeze-gel. Based on the results of breaking and creep tests, strain and retardation time (λ) of cold-gel were higher than those of heat-gel and freeze-gel. Both elasticity and smoothness of cold-gel on sensory evaluation were significantly higher than those of heat-gel and freeze-gel. The water-holding capacity of cold-gel was increased with time during cold storage, and was in well agreement with changes of gel strength. Line-width value of NMR spectra on cold-gel decreased with the elapse of time during cold storage. The gels heated or frozen after treatment of cold storage had higher strain than gels heated or frozen without cold storage. Based on a SEM observation, the unit of mass on microstructure of cold-gel was bigger than that of heat-gel or freeze-gel. It was suggested that the unit size of microstructure of cold-gel was responsible for elasticity of the gel.